When farmers first began to apply chemical pesticides in Asia, they found them to be very effective in controlling insect pests, diseases and weeds. Unfortunately, this effectiveness did not last long. Pest resistance soon appeared, and became so widespread that many pesticides became ineffective. Over time, the health hazards of pesticides also became apparent. Chemical pesticides are still seen as a useful technology, but one which needs careful management if it is to be safe and effective.
In 1997, FFTC and the Asian Productivity Organization (APO) carried out a regional survey of the production and use of agricultural chemicals in the region. The results of the survey showed changes in patterns of pesticide use in recent decades, mostly in the direction of an increasing trend. The survey also showed that some countries lack a strong national system of pesticide registration, or clear regulations governing chemical applications. This suggests that chemical use in Asian countries may still be immature, and that there is a great need for detailed data if maximum safety and effectiveness are to be achieved.
In December 1998, FFTC held an international seminar as a follow-up to the survey. Topics discussed at the seminar included discuss current patterns of production and use of chemical pesticides in Asia, government policies concerning agricultural chemicals, and major problems faced by farmers in using these chemicals effectively.
For some decades, there has been a pro-pesticide bias in research and extension. This is now giving way to a general bias in favor of IPM. However, although IPM policies are popular, in practice IPM programs are difficult to implement. They are now becoming even more difficult as countries in the region adopt a free market approach to pesticide sales and distribution. This makes it almost impossible to coordinate pesticide use over a wide area, a basic strategy in IPM for resistance management.
Many of the harmful effects from applying chemical pesticides come not so much from pesticide
use as from pesticide
misuse. This includes overapplication, repeated application of the same pesticide, poor application technology, and even the use of pesticides to catch fish. It was suggested that rather than focus on new technologies such as biological control and IPM, it might be more effective to make sure that pesticides are used properly.
This includes the improvement of application technology and sprayers, especially for low-income farmers. The condition and quality of the sprayer, and especially the nozzle, are very important. Under the best of circumstances, it is not easy for farmers to apply a fixed volume of chemical spray evenly over a fixed area. If the application technology is poor, farmers tend to apply far too much pesticide.
An efficient monitoring system which regularly tests food items for pesticide residues is a strong incentive for farmers to use chemicals wisely. Indeed, unless contaminated shipments can be identified, farmers may not know or care whether the produce they are selling contains pesticide residues. However, the facilities needed for chemical testing are expensive, while there is some controversy over the accuracy of the cheaper bioassay procedure. One promising approach is HACCP - Hazard Analysis at Critical Control Points. This looks at the whole chain of pesticide distribution and use, and selects the particular points where action is feasible and will make an impact.
Part of the IPM approach is the use of non-chemical control methods. Farmers themselves share a great deal of valuable indigenous knowledge about botanical resources which help control pests. However, because a biological product is `natural' does not mean that it is safe.
The use of natural enemies (predators and parasitoids) is widely accepted, as is the use of insect sex pheromones, and entomopathogenic microbes and fungi. More controversial are transgenic crops which incorporate genes from other species to enhance disease and pest resistance. Because this technology is new, we cannot predict its long-term effects. Our experience with chemical pesticides and other technologies has taught us that powerful new technology often carries unforeseen and serious side-effects. There are fears that the side-effects of transgenic crops may be more widespread and damaging than those from chemicals, and more difficult to control.
Resistance management is a key concept in pest control. Usually this involves repeated change of the control agent
Bacillus thuringiensis) genes in transgenic crops. Although b.t. resistance is known to occur after repeated applications of b.t. products, the effect seems to be due to a number of recessive genes. If applications stop, resistance generally disappears after a few months. The presence of b.t. genes in crop plants would mean that insect pests are constantly exposed to b.t.. This may cause permanent and irreversible resistance.
Biological pesticides have many advantages. They are low-cost, the effect is self-sustaining, and they should not harm non-target species. They are also much cheaper to develop than new chemical pesticides. An important recommendation of the meeting was that the development of biopesticides should focus on indigenous biological resources, and on low-cost, on-farm production of these control agents.
As with fertilizers, application rates for chemical pesticides are highest in industrialized countries, reflecting the low cost of farm inputs in relation to farm incomes. Application rates in Vietnam, for example, are around 1.0 kg/ha (a.i.), compared to 11.8 kg/ha in Korea and 19.4 kg/ha in Japan. Application rates in Taiwan ROC are even higher than in Japan. In all three industrialized countries, pesticide use has been declining in recent years. The same is also true of Iran, where pesticide use fell by 74% between 1990 and 1995. Improved cultural practices and biological control combined with minimum levels of pesticide gave very effective pest control. The fact that yields in Iran remained stable over this period demonstrates the importance of IPM programs. In contrast, levels of pesticide use in other less industrialized countries generally show an increasing trend, although consumption levels are still relatively low.
When a country is in the early stages of pesticide use, insecticides tend to be the most common type of pesticide used. Over time there is a tendency for herbicides to grow more important, as farm incomes rise and farm labor for manual weeding becomes more expensive.
Japan and India are important producers of technical grade pesticides. Korea and Taiwan also produce technical grades. Most of these are generic pesticides (i.e. the patent has expired), which can be produced at a low cost. Most other countries in the region import technical grades and process them locally into required formulations. The need was expressed for safer formulations, such as WDG granules rather than wettable powder.
In the 1970s and 1980s, many governments played a major role in pesticide production and distribution. During the 1990s, there was a change in policy. Most countries now leave production and marketing to the private sector. This has the advantage that farmers can buy a greater range of chemical products. The main disadvantage is that most of the information farmers receive about a pesticide comes from the company which makes and sells it, via the retailer. Most village pesticide dealers are not well informed about what pesticide to use for a particular pest problem, or how to use it safely. Since they are interested in selling as much of their products as possible, they have no interest in minimizing pesticide use.
Much the same situation is found at a national and international level. Chemical companies tend to release only positive data from toxicity tests. Furthermore, much of the data from toxicity tests is regarded as confidential commercial information which cannot be made public. This means that national governments are forced either to accept the company's data, or carry out their own tests to find out how toxic a new product may be, and whether it has long-term adverse effects.
It was recommended that training courses should be held in pesticide regulation and monitoring for government staff working to improve pesticide safety. Another recommendation was that training should be expanded to include village level retailers, while farmers should be able to get more information from the mass media. Labelling of products also needs improvement: labels should be clear, informative and in the local language. Information flow would also be greatly improved if countries in the region shared their toxicity data. In particular, this would benefit small countries who have limited funds and personnel available for testing new products.
Resistance management is of major importance, so that newly introduced pesticides may keep their effectiveness as long as possible. Chemical companies tend to aim at maximizing their share of the market. If they are successful in doing this, the result is heavy dependence on a single pesticide, which tends to promote resistance. An important recommendation of the seminar was that countries in the region should share data on pesticide resistance.
There was considerable discussion of the use of banned and restricted pesticides, particularly the group of 18 very hazardous pesticides popularly known as the "Dirty Dozen". Most countries represented in Asia at the symposium have banned some or all of these pesticides already. However, one problem is that some of the chemicals, particularly DDT, are widely used for mosquito control and other public health programs. If a pesticide is available but approved for a restricted use, it is often purchased for other non-approved agricultural uses.
It is important to consolidate the various agencies concerned with pesticide production and use.
Consumer resistance to the use of chemical pesticides, together with the growing problem of pest resistance, is encouraging farmers to adopt organic farming methods, or production systems which make minimal use of chemicals. IPM is a popular concept, but even in countries which are promoting IPM, the percentage of farmers using this type of pest control is fairly small. IPM is technically difficult, and requires coordinated action by large numbers of farmers. The tendency for production and distribution of pesticides to move out of government control and into the private sector may make IPM programs even more difficult in future. However, the success of IPM programs in Indonesia and elsewhere in the region does indicate their potential in future pest and disease control programs. For the present, a more practical goal might be to improve the use of chemical pesticides so that farmers are making safe and effective use of relatively non-toxic formulations.
The seminar showed clearly the potential benefits of regional data collection and data sharing. A sound database would be an important aid in identifying issues and constraints when policies are being formulated to reduce the incorrect and excessive use of pesticides, both in agriculture and in public health programs. There is particular interest in exchanging information on pesticide registration, biological pesticides, banned and restricted chemicals, and data on pesticide resistance. Regional cooperation would also be valuable in improving laboratory procedures and harmonizing technical standards.
Location: Tokyo, Japan
Date: December 9-15 1998
No. Participating Countries: 19 (Bangladesh, Fiji, India, Indonesia, Iran, Japan, Korea, Malaysia, Maldives, Mongolia, Myanmar, Nepal, Pakistan, Philippines, Sri Lanka, Taiwan ROC, Thailand, USA, Vietnam)
No. Papers: 23
No. Participants: 28 plus observers
Co-sponsor: Asian Productivity Organization (APO)
1. Evaluation of pesticide residue analysis methods for food safet
y- Sue-Sun Wong
2. Developing cost-free technology to manage soybean insects in Indonesia
- Atsushi Naitoh
3. Recent progress in the development and application of bio-pesticides, with special emphasis on insect control in Taiwan
- S.S. Kao
4. Recent progress in integrated pest management for vegetables
- E. Yano
5. New perspectives in the controlled use of pesticides
- Tjaart Shillhorn
6. Presentation and discussion of the regional report
- Gwo Chen Li
Plus Country Papers about: Bangladesh, Taiwan ROC, Fiji, India, Indonesia, Iran, Korea, Maldives, Malaysia, Mongolia, Myanmar, Nepal, Pakistan, Philippines, Sri Lanka, Thailand, Vietnam
Figure 1 Biological Pest Control: Green Rice Leafhoppers Infected by Fungal Pathogens (Beauveria Bassiana (Right), Metarhizium Anisopliae (Left))
Figure 2 Many Asian Farmers Are Not Aware of the Risks Involved in Applying Pesticides